1. Statement of the Technical Field
The invention is relevant to the field of antennas, and, in particular, to methods of aligning antennas to a particular target, both in commercial and military settings.
2. Description of the Related Art
Currently, antennas in the field, both for military and for commercial applications, must be manually aligned. This involves a process of sending a “ping” to the target antenna and listening for a response transmission. This process is repeated until the antenna is positioned where the signal strength of the transmission from the target transmitter is highest. Likewise, if the target transmitter is a satellite that is continuously transmitting, such as a satellite used for the transmission of satellite television signals, the antenna is pointed in the general direction of the satellite and its position fine-tuned using a signal strength meter. The antenna is usually considered to be aligned when pointed in a direction that results in the highest signal strength being received from the target transmitter.
Auto-pointing antennas are also available, but currently work on the same principle of changing the antenna position until the greatest signal strength is measured for signals received from the target. Auto-pointing antenna systems generally tend to be used in larger systems, such as those which are mounted in military or commercial vehicles.
Because communications satellites are typically in geosynchronous orbit, aligning an antenna to a satellite involves calculating the azimuth (side-to-side) and elevation (up-down) angles of the satellite. Once this information has be determined, the antenna position can be adjusted so that the boresight of the antenna is aligned with the particular satellite. The azimuth and elevation angles needed to align the antenna are dependent on the latitude and longitude of the antenna and the particular satellite that the dish needs to point to. As positions of satellites with respect to the Earth are known, there are software programs readily available that will calculate the azimuth and elevation angles for a particular satellite, given the latitude and longitude of a terrestrial antenna. These software programs can provide a rough azimuth and elevation angle needed for positioning of the antenna. The positioning of the antenna can then be fine-tuned using the signal strength method described above.
The process for aligning two land-based antennas is similar to the process used for aligning a terrestrial antenna with a satellite. The approximate location of the target antenna must be known with respect to the current position of the local antenna being aligned. Because antenna alignment requires line-of-sight, it is often possible to obtain a rough alignment of a terrestrial target antenna by actually sighting the target antenna. The alignment can then be fine-tuned using the signal strength method.
One drawback of the current method of aligning antennas, particularly in a military setting, is that alignment requires a signal to be sent to the target satellite or target ground-based antenna. In certain situations, a signal may also be sent by the target antenna to the local antenna which is being aligned. This process may give away the position of one or both of the antennas involved in the alignment process, even before any substantive transmission takes place. In situations where it is desirable to remain covert, this can be a distinct disadvantage.